Electric Charges and Fields — Physics STD 12 Science — Question

The direction of line of magnetic field of bar magnet is

(a) From south pole to north pole

(b) From north pole to south pole

(c) Across the bar magnet

(d) From south pole to north pole inside the magnet and from north pole to south pole outside the magnet

Two identical capacitors A and B are charged to the same potential V and are connected in two circuits at t = 0 as shown in figure. The charges on the capahltors at a time t = CR are, respectively:

X-rays are :

For depositing 1 gm of Cu in copper voltameter on passing 2 amperes of current, the time required will be (For copper  Z = 0.00033 gm/C)

(a) Approx. 20 minutes

(b) Approx. 25 minutes

(c) Approx. 30 minutes

(d) Approx. 35 minutes

A hollow sphere and a solid sphere having same mass and same radii are rolled down a rough inclined plane:

1. The hollow sphere reaches the bottom first.
2. The solid sphere reaches the bottom with greater speed.
3. The solid sphere reaches the bottom with greater kinetic energy.
4. The two spheres will reach the bottom with same linear momentum.

In a coaxial, straight cable, the central conductor and the outer conductor carry equal currents in opposite directions. The magnetic field is zero:

1. Outside the cable.
2. Inside the inner conductor.
3. Inside the outer conductor.
4. In between the tow conductors.

The maximum focal length of the eye-lens of a person is greater than its distance from the retina. The eye is:

1. Always strained in looking at an object.
2. Strained for objects at large distances only.
3. Strained for objects at short distances only.
4. Unstrained for all distances.

A combination of two thin lenses of the same material with focal lengths  and , arranged on a common axis minimizes chromatic aberration, if the distance between them is

(a)

(b)

(c) (

(d)

The number of turns in the primary coil of a transformer is 200 and the number of turns in the secondary coil is 10. If 240 volt AC is applied to the primary, the output from the secondary will be

(a) 48 V

(b) 24 V

(c) 12 V

(d) 6 V